Hydraulic liquid having a comparatively small change in viscosity



Patented Nov. 5, 1 946 UNITED STATES PAT m- OFFICE HYDRAULIC LIQUID HAVING A COMPARA- TI VELY SMALL CHANGE IN VISCOSITY John D; Morgan, South Orange, N. 1., assignor to: Cities Service Oil Company, Hillside; N. l, a corporation of Pennsylvania No Drawing. Application March 2, 1942, Serial No. 433t02'0 F. to 200 F; It is. very desirable that the fluid which is to be. used in the recoil cylinders should have a; substantially uniform viscosity so that. the

recoilcan be equally controlledregardless of the temperature under which it is operated. Such a liquidmust have a low freezing point and: should change comparatively small amounts-.in-viscosity from the lowest temperature up to the highest temperature. shock absorbers and such a liquid can advantageously be used in the operation of hydraulic brakes.

A liquid suitable for the purposes outlined above has. the. following preferred formula:

Percent by volume- Tributyl phosphate 97.75 Extreme'pressure agient (tricresyl phosphite or Polane) 1.00 Lead naphthenate 1.00 Santolube #261 0.25

In the above formula triethyl phosphate may replace the tributyl phosphate.

It has been found that the tricresyl phosphite, the lead naphthenate and the Santolube #261 are quite soluble in the tributyl phosphate, These ingredients, however, are not so soluble in the triethyl phosphate and it has been desirable, therefore, to replace part of the triethyl phosphate with furnace oil or kerosene to help hold the lead naphthenate, the Santolube #261 and the tricresyl phospbite in stable solution. For example if 75 percent of triethyl phosphate is used with 22.75 percent of furnace oil or kerosene, a liquid having a comparatively uniform viscosity characteristic may be produced. In all of these compounds the lead naphthenate acts as a corrosion resistant agent. The Santolube #261 acts as a corrosion resistant agent, and antioxidizing agent, and a pour point depressant agent. The Polane and tricresyl phosphite act to give load carrying capacity to the oil, that is provide extreme pressure lubricating qualities.

It has been found also that dichlorethyl ether This same principle applies to on amyl acetate may be used with the tributyl phosphate or. tr'iethyl" phosphate in making up -I a stable;.uniform viscosity fluid;

Santolube #261 is an additive.- commonly used inv modifyinglubricating oi ls;.an;d".isv a sulfurized tin salt ofianalkylphenol carboxyli'c acid,.manufactured under Patents Nos, 2,197,834; 2,1 97,835;.1 22562441; anda2;2'57-',751.. This productl is alsorefeiiredi to as a metallic derivative of? an alkylated carboxylic acid containing combined. tin and sulfur, The; percentage of tin in the additive agent. is percent by weight and the sulfur is. 0.8 percent-by weight. Thisproduct acts. as apour point depressant and antioxidant, and acts also asan': inhibitor for preventing corrosion to metals withwhich the hydraulic liquid comes' in contact. In the liquid ofthepresent invention itisimportant that the liquid should not corrode the partsin: Which-it operates.

The improved liquid of the present invention which is suitable for use in hydraulic apparatus. has' a low freezingpointof, for example, below' minus 50 F..or min-us FR,v and preferably has a-Saybolt Universalzv-iscosity in the range of from 300seconds at minus 40 F, to 35 seconds at 200 having a base-of tributyl: phosphateishow the. following Saybolt Universal viscosity characteristics.

Seconds 40 F 278 0 F F 36 200 F 30 For the same formula replacing tributyl phosphate With triethyl phosphate, the Saybolt Umversal viscosity tests are as follows:

In a composition using triethyl phosphate and furnace oil in the above formula for tributyl phosphate the following viscosity characteristics are obtained:

Seconds -40 F 263 100 F 35 200 F 30 With a liquid containing tributyl phosphate 75 percent and amyl acetate 22.75 percent in place of the tributyl phosphate of the above formula Tests on the preferred uniform viscosity-fluid:

3 the Saybolt Universal viscosity characteristics are:

Seconds -40 F 119 100 F 33 200 F 28 4 below about minus 50 F. and a comparatively small change in viscosity in the temperature range between about minus 40 F. and about agent, the anticorrosion agent and the pour point depressant agent may be Varied from one-tenth to one percent without materially changing the physical properties of the liquid. The proportions given above are those proportions which appear to give th most economical mixture of the ingredients which will give the desirable hysical characteristics.

Polane, referred to above, is a commercial product on the market, which is chloromethyl stearate.

The preferred form of the invention having been thus described, what is claimed as new is:

1. A hydraulic liquid having a freezing point below about minus 50 F. and a comparatively small change in viscosity in the temperature range between minus 40 F. and 200 F., consisting substantially entirely of a trialkyl phosphate having dissolved therein about 1% by volume of a corrosion-resisting agent and about 0.25%

200 F., consisting substantially entirely of a trialkyl phosphate having dissolved therein about 1% by volume of lead naphthenate and from about 0.1 to about 1% by volume of a sulfurized tin salt of an alkyl phenol carboxylic acid.

4. A hydraulic liquid having a freezing point below about minus F. and a comparatively small change in viscosity in the temperature range between about minus 40 F., and about 200 F., consisting substantially entirely of a trialkyl phosphate having dissolved therein approximately 1% by volume of a corrosion-resisting agent, approximately 1% by Volume of an extreme pressure agent, and from about 0.1% to about 1% by volume of a sulfurized tin salt of an alkyl phenol carboxylic acid.

5. A hydraulic liquid having a relatively low freezing point and a comparatively small change in viscosity in the temperature range between about minus 40 F. and 200 F., comprising about 97.75% by volume of tributyl phosphate, about 1% by volume of an extreme pressure agent, about 1% by volume of lead naphthenate, and about 0.25% by volume of a sulfurized tin salt of an alkyl phenol carboxylic acid.

6. A hydraulic liquid having a low freezing point and a comparatively small change in viscosity in the temperature range between about minus 40 F. and about 200 F., comprising about 97.75% by volume of triethyl phosphate, about 1% by volume of tricresyl phosphite, about 1% by volume of lead naphthenate, about 0.25% by volume of a sulfurized tin salt of an alkyl phenol carboxylic acid.

7. A hydraulic liquid, consisting essentially of a trialkyl phosphate having dissolved therein a corrosion-resisting agent in sufiicient proportion to prevent corrosion of the metals with which the hydraulic liquid comes in contact.

8. A hydraulic liquid, consisting essentially of a tributyl phosphate having dissolved therein a corrosion-resisting agent in suificient proportion to prevent corrosion of the metals with which the hydraulic liquid comes in contact.

JOHN D. MORGAN. 

